Hydraulic jack for the tensioning and anchoring of the reinforcement metal in a reinforced concrete construction



Oct. 30, 1 956 J. a 8. .1. J. BOUVY EETAL 2,763,810

HYDRAULIC ,mcx FOR THE TENSIONING AND ANCHORING 0F rma REINFORCEMENT-Fil'ad 'duly so. 1953 METAL JENNA REINFORCED CONCRETE CONSTRUCTION 4Sheets-Sheet 1 INVENTOR-S Jncqwss Jaw BER/V4190 JasEPfl Jwons 60v BYALL-34w;- Iron/u 91 QOW' -41 M Oct. 30, 1956 J. J. B. J. J. BOUQVIIY'ETAL 2,768,810

HYDRAULIC JACK FOR THE 'rsnsroumc AND-QANCHORING OF THE REINFORCEMENTMETAL IN A REINFORCED CONCRETE CONSTRUCTION Filed July 30. 1953 4Sheets-Sheet 2 30, 1956 J. J. B. J. J. BOUVY ETAL 3 v HYDRAULIC JACK FORTHE TENSIONING ANDANCHOR-ING OF'..THE smnwoacmmw METAL an A REINFORCED=JCONCRETE CON-STRUQTI&

4 Sheets-Sheet 3 Filed July 30, 1953 INVENTORS: Jlqcqwes JEAN BBP/Yflkl?mp J5me Baum #455197 Kama/N Y MW, aw M 6% 0d. 1956 J. J. B. J. J. BOUVYETAL 2,763,810

HYDRAULIC JACK FOR THE TENSIONING AND ANCHORING OF THE REINFORCEMENTMETAL IN A REINFORCED coucnsws CONSTREJCTION Filed m so 1953 v 4Sheets-Sheet 4 B) $0 4m &

NwE mdE United States Patent HYDRAULIC JACK FOR THE TENSIONING AND ANCHORING OF THE REINFORCEMENT METAL IN A REINFORCED CONCRETE CONSTRUCTIONJacques Jean Bernard Joseph Jerome Bouvy and Albert Komijn, The Hague,Netherlands Application July 30, 1953, Serial No. 371,272 Claimspriority, application Netherlands July 30, 1952 6 Claims. (Cl. 254-29)The invention relates to a hydraulic jack for the tensioning andanchoring of the reinforcement metal in a reinforced concreteconstruction with pre-tensioned reinforcement comprising a cylinder witha main piston and an auxiliary piston. With this jack the wires of thereinforcement are adjusted in pairs in a slot arranged in the cylindersurface by means of wedges, whereby the main piston supports against ananchoring-block. Then liquid is supplied under pressure in a spacebetween the main piston and the cylinder, causing a displacement of thecylinder with respect to the anchoring block and the wires aretensioned. Then liquid is brought under pressure into said space betweenthe main piston and the auxiliary piston and so the auxiliary pistonpresses the anchoring plug into the anchoring block, anchoring in thisway the wires of the reinforcement. At last the hydraulic pressure inthe cylinder is let off and the tension in the reinforcement-wiresextending from the anchoring block is relieved and the wires areloosened from the cylinder. This last manipulation is executed by meansof a hammer, with the aid of which the wedges are beaten away, which hasto be done by a skilled laborer, for, if perchance by a miss a wire istouched, there is a risk that the friction of the tensioned wire in theanchoring block is loosened by the fibrillation and the wire will losepart of its tension.

Another disadvantage of the jacks heretofore employed is the fact thatthe wires of the reinforcement located between the anchoring block andthe wedges on the cylinder are contacting the extension piece of themain piston, causing an undesired friction during the tensioning of thewires.

Yet another disadvantage resides in the way of measuring the extensionofthe wires. Up till now this has been done by measuring thedisplacement of marks made on the wires before they are tensioned. Thismeasurement of the displacement can take place only insufficiently bythe means used up till now.

Another disadvantage is the possibility that by operating in impropersequence the taps through which the pressure fluid is supplied andwithdrawn disturbing faults are made, for instance the anchoring of thewires before they are tensioned, and the like.

The invention has in view to meet the mentioned disadvantages.

According to the invention the jack is so constructed and provided withappliances that the successive manipulations of the tensioning of thewires of the reinforcement, the anchoring of the anchoring plug and theloosening of the wedges takes place automatically in the abovementionedsequence.

According to another feature of the invention a ring shaped liquidchamber is arranged between the cylinder and the main piston, saidliquid chamber is adapted to be brought in connection with the supply ofthe pressureliquid so that the cylinder and the main piston can undergoa relative displacement as a result, the usual spring with the resultingfriction losses can be eliminated.

According to another feature of the invention the liquid chambers in thejack are in communication with a controlling apparatus being soconstructed that only one of the chambers is in communication with thepressure liquid, the other chambers either being in open communicationwith the outlet of the liquid, or being closed off.

Other features and characteristics appear in the description and theclaims.

The drawing, purely illustrative, represents one form of executionaccording to the invention, wherein the Figures 1-3 show, partially insection, three different stages of a jack with controlling apparatusduring the action, and Figs. 4 to 10 are sectional views taken alonglines 4-4 to 10-10 of Fig. 3, respectively.

The jack 1 comprises a cylinder 2, wherein a main piston 3 is axiallymovable. In an extension piece 4 with jackhead 42, firmly connected withthe main piston 3 an auxiliary piston 5 is axially movable. In the jackthree liquid or pressure chambers 6, 7 and 8 are provided, theliquid-chambers 6 being located between the top of the main-piston 3 andthe end of the cylinder 2, the liquid chamber 7 being arrangedringshaped around the main piston 3 and limited by this main piston, thecylinder 2 and the walls 9 and 10 respectively of the cylinder and themain piston. The liquid chambers 6, 7 and 8 are by means of channels 11,12 and 13 bored in the main piston or arranged otherwise in it, and bymeans of flexible tubes 14, 15 and 16 connected with the junction pieces17, 18 and 19 on the cylinder 20 of the controlling device 21. Thecylinder 20 is provided with a junction piece 22 for the supply of thepressure liquid and a junction piece for the outlet 23 of the liquid.

In the cylinder 20 a piston 24 is axially movable by a motor or the like(not shown), while four ringshaped chambers 25, 26, 27 and 32 beingformed by peripheral ridges 29, 30 and 31 fitting in the innerwall ofthe cylinder. Chambers 28 and 33 are provided in the piston 24. Thecylinder 2 is provided with a collar piece 34 with slots for the wire 35of the cable and the wedges 36. On the main piston 3 a plurality of camsor ears 37, equal in number to the wedges 36 are arranged spaced atregular distances over the circumference of said main piston. These earsare preferably so arranged that their shock surfaces are placedstaggered relative to each other, for instance so that always two earsextend radially opposite each other, having their shock surfaces in aplane perpendicular to the axis of the jack.

By this arrangement only two wedges 36 being located radially oppositeeach other are pressed away at the same time by a displacement of themain piston 3 with respect to the cylinder 2 to the right in thedrawing, so causing a gradual relaxation of the wires.

The auxiliary piston 5 is movable in the extension piece 4 to the left,in the drawing, against the action of a spring 38.

The anchoring block is indicated at 39 and the anchoring plug at 40.

An elongation measuring device 41 is connected to the cylinder 2.

The device works as follows:

After the jack 1 with the jackhead 42 has been placed against theanchoring block 39 in the position shown in Figure 1, with plug 40 beingmounted in the mouthpiece on the extension piece 4 and bearing looselyin the anchoring block 39, the wires 35 are fastened in the usual way inpairs by the wedges 36. The extension piece 4 is pressed against theanchoring block 39. In this phase the piston 24 of the controllingdevice is in its most right hand position. Now the piston 24 is broughtin the position as indicated in Fig. l, enabling the liquid to be pumpedthrough the junction piece 22, the liquid chamber 25, the channel 28,the junction piece 17, the tube 14 and the channel 11 into the liquidchamber 6, causing the cylinder 2 to be moved with respect to the mainpiston 3, bearing against the anchoring block 39 in a direction awayfrom this anchoring block, so tensioning the wires 35 of the cable. Thedegree of elongation can be accurately read on the elongation measuringdevice connected to the cylinder. This elongation has to correspond inaccordance to the kind of steel, which is used, with the pressure readon the manometer of the liquid-pump.

When the desired elongation and the according pretension has beenobtained, the piston 24 is moved to the left in the position as shown inFig. 2. In this position the ridge 30 is laying in front of the junction17, preventing the liquid under pressure in the liquid chamber 6 fromflowing away so that the relative disposition of the piston 3 and thecylinder 2 remains unchanged. In this position of the piston 24 liquidis pumped via the junction 22, the liquid chamber 25, the channel 23,the liquid chamber 32, the junction 19, the tube 16 and the channel 13into the liquid chamber 8 so pressing the auxiliary piston 5 against thepressure of the spring 38 in the direction of the anchoring block and sopressing the anchoring plug 40 firmly between the wires and anchoringthem in the anchoring block.

Next the piston 24 is moved to the position as shown in Fig. 3. In themeantime the liquid in the chamber 6 is flowing away via the channel 11,the tube 14, the junction 17 and the chamber 26 and the liquid in thechamber 8 is flowing via the channel 13, the tube 16, the junction 19,the chamber 26 and both liquids are flowing together off through thechannel 33 and the junction 23?, pressure liquid is pressed via thejunction 22, the chamber 25, the channel 28, the chamber 32, thejunction 18, the tube 15 and the channel 12 into the liquid chamber 7,causing the walls 9 and 10 to be moved from each other and so displacingthe main piston 3 into the cylinder 2. During this displacement the ears3'"! approach the wedges 36 and press them under the influence of theliquid pressure without shock to the right, relaxing the wire endsbehind the anchorage. Therefore every time two wedges located radiallyopposite each other are loosened simultaneouslyand in consequence of thestaggering location of the shock surfaces, this loosening takes placepair after pair and consequently the relaxation is gradual.

What we claim is:

l. A hydraulic jack for tensioning and anchoring the wire reinforcementcable in a concrete construction with pre-tensioned reinforcement, whichcomprises: a main cylinder; a first chamber for liquid in said maincylinder; a. main piston in said cylinder, an auxiliary piston slidablymounted in said main piston; an anchoring block 7 and a cooperatinganchoring plug for anchoring said tensioned reinforcement Wires; meansconnecting said cylinder with said reinforcement wires, and saidauxiliary piston with said anchoring plug, whereby movement of saidcylinder relative to said main piston acts to tension said wires, andmovement of said auxiliary piston relative to said piston serves toanchor said anchoring plug in said anchoring block, whereby saidpre-tensioned wires are securely held; a further ring-shaped liquidchamber defined between the peripheral wall of a reduced portion of saidmain piston and the inner wall of said cylinder, said ring-shapedchamber being adapted to receive liquid pumped therein, said liquidchambers being in communication, whercby when liquid is pumped into saidringshaped chamber and out of said first chamber in said main cylinder,said main piston is moved relatively to said main cylinder in adirection such that said main piston enters into said main cylinder and,at the same time, said auxiliary piston is loosened from said anchoringplug.

2. The hydraulic jack as defined in claim 1, wherein a plurality ofwedges serve to fasten said wires to said main cylinder, and whereinmeans are provided for controlling, without possibility of error, thesequence of desired operations in said tensioning and anchoring,

said means controlling the flow of liquid to and from said liquidchambers in said main cylinder and said ringshaped chamber whereby, uponmoving said main piston in a single direction, the following sequence ofoperations occurs; first, said wires are tensioned; second, said wiresare anchored; and third, said wires extending beyond said anchoring plugare loosened by removal of said wedges.

3. A hydraulic jack for tensioning a wire cable in a pre-tensionedstructure, comprising in combination; a cylinder provided with slots forreceiving the strands of said cable, a main piston extending into saidcylinder and, defining therewith first and second chambers, admission offluid into said chambers selectively eflecting relative displacementbetween said cylinder and said main piston in opposite directions, anauxiliary piston defining a third chamber with said main piston,admission of a fluid into said third chamber effecting displacement ofsaid auxiliary piston relative to said main piston, and first, secondand third duct means communicating with said first, second and thirdchambers, respectively, for admission of a fluid thereinto and for exitof said fluid therefrom, whereby following disposition of said cablestrands in said cylinder slots, admission of fluid into said firstchamber effects tensioning of said strands, admission of fluid into saidthird chamber displaces said auxiliary piston relative to said mainpiston for anchoring said tensioned strands in said structure, andadmission of fluid into said second chamber empties said first chamberfor releasing the ends of said strands held in said slots of saidcylinder.

4. A jack as defined in claim 3, in which said slots of said cylinderare set in balanced groups, said jack being further provided with wedgesfor holding said strands in said slots, and a cam member operativelyconnected with said main piston, said cam member being provided withears corresponding in number and disposition to the slots of eachcylinder group, whereby admission of fluid to said second chamber causessaid ears to enter said slots and remove said wedges, the grouping ofsaid slots ensuring an even release of tension on the ends of said cablestrands.

5. A jack as defined in claim 4, in which each group is composed of twodiametrically opposite slots, said cam member thus being provided withtwo diametrically op posite ears.

6. A jack as defined in claim 3, including control means for said ductmeans, said control means comprising a further cylinder and a furtherpiston displaceable therein, said further cylinder being provided withinlet and outlet means for a fluid and with apertures communicating withsaid first, second and third duct means, respectively, said furtherpiston controlling communication between said inlet and outlet means onthe one hand and said apertures on the other hand, whereby displacementof said further piston within said further cylinder sequentially causessaid first chamber to communicate with said inlet means to tension saidstrands, said third chamber to communicate with said inlet means toanchor said tensioned strands, and said second chamber to communicatewith said inlet means while said first and third chambers communicatewith said outlet means, to thereby fill said second chamber with fluidand empty said first and third chambers of fluid for releasing the endsof said cable strands held in the slots of said cylinder.

References Cited in the file of this patent UNITED STATES PATENTS2,328,033 Schorer Aug. 31, 1943 2,371,882 Freyssinet Mar. 20, 19452,637,895 Blaton May 12, 1953 FOREIGN PATENTS 543,249 Great Britain Feb.16. 1942

